Pyridine derivative and processes for the manufacture of same



Patented Nov. 12, 194

2,410,943 ICE PYRIDINE DERIVATIVE AND PROCESSES FOR THE MANUFACTURE- OF SAME Max Heifer, Nutley, N. J., assigr or to Hoifmann- La Roche, Inc., Nu tiey, N.

New Jersey 91 .1 cpmc aii of No Drawing. Original applicationseptember 2, 1941, Serial No. 409,298. Divided and this, ap plication May 11, 1945, Serial No. 593,318 In Switzerland September 2, 1940 2 Claims. 1. The present invention concerns the synthesis of vitamin Be (adermin) of the formula:

, onion \NfCHIS I have found that the compound 2-methyl-4- phenoxymethyl--cyano-6-hydroxy pyridine-3- carboxylic acid (I) is an advantageous starting material for this synthesis. It is prepared by successively treating the condensation product, obtained from malonic acid dinitrile, phenoxyacetaldehyde-hydrate and acetoacetic ester, with an acid and a reducingagent, in accordance with Example 3 of my co-pending application S. N. 409,298, filed September 2, 1941, entitled Hydroxy-pyridine derivatives and process for the manufacture of same.

By treatment with phosphorus-pentachloride the 2 methyl-4-phenoxymethyl-5-cyano-6-hydroXy-pyridine-3-carboxylic acid (I) is con-, verted into 2-methyl-4-phenoxymethyl-5-cyano- 6-chloro-pyridine-3-carboxylic acid chloride (II) and hydrazine caused to act thereon in the presence of free alkalis. The reaction can be illustrated by the following formulae:

It issurprising that it is possible to introduce the hydrazine radical in the side-chain in posi tion 3 without the halogen reacting in the a-position, although it is known that -halogen substituted-pyridine derivatives can react easily with hydrazine (Journal. of the Chemical Society of London, "vol, 103, year 1913, page1978; vol. 107, year 1915, page 691; Monatshefte fur Chemie, vol. 36, year 1915, page 736), The desired reaction consequently only succeeds in presence of free alkalis. Curiously enough, the hydrazide formed thereby goes into the alkalin solution,

from which it can be precipitated by neutralization of the alkali by meansoiflfree acids, andmonium vsalts or acid salts.

The 2-methyl-4-phenoxymethyl 5 cyano-6 chloro-pyridine- 3 carboxylic acid hydrazid 2 (I11) thus obtained is convertedinto the azide by nitrous acid or materials developing nitrous acid during the reaction, and the azideboiled withalcohols eithervafter its isolation or in the reaction mixture to for-m2-methyl-3-carbalkoxyamino-4- phenoxymethyl-5-cyano-6-chloro pyridine.

This compound can be converted; in one step into 2Fmethyl-3-carbalkoxyamino 4 phenoxymethyl-5-aminomethyl-pyridine. The, hydrogenation of the cyano group to the aminomethyl group; has often been described in the literature. However, the Working is thereby effected almost exclusively with palladium or platinum as catalystin acid solution. On working inneutral solution and with nickel catalysts, on the other hand, secondary amines are mostly obtained (Helvetica Chimica Acta, vol. 5, year 1922, page 937; Vol. 6, year 1923, page 880; vol. 8, year 1925, page 848). It has now been found that Z-methyl-B-carb: alkoxyamino-4- phenoxymethyl -5-cyano-6-chloro-Wridine, under suitable conditions, can also.

be reduced to the corresponding primary'amine with nickel catalysts. Thereby, the chlorine atom in position 6 is simultaneously replaced by hydrogen. This course of the reaction could not be anticipated, for no case'has become known so .far Where a chlorine atom adhering. to a pyrr- I idine radical has been replaced by hydrogen by means of nickel as a catalyst. It was rather to be expected that chlorine would be obstruc-,

tive during the hydrogenation (Adkins Reactions of Hydrogen with Organic Compoundsnover Copper-Chromiumoxide and Nickel Catalysts, Wisconsin, year 1937, page 54; Schwoegler, Journal of theAmerican Chemical Society, vol. 61, year 1939, page 3502). o

The 2-methy1-3-carbalkoxyamino-4-phenoxymethyl-5-aminomethyl pyridine is converted into Z-methyl-3-carbalkoxyamino 4- phenoxymethyl-5 hydroxymethyl-pyridine (IV), by cause ingoto act thereon nitrous acid or materials developing nitrous acid in presence of water.

The'following formulae illustrate the conversionofsaid compoundIV into adermin:

oniooim HQHzG Nncooa \MOHS,

(lJH2Br I 1 onion; BrHQC NHiHBr Homoon H l H I N cHa $20 N cHa v. VI'

It has been found that in the 2-methyl-3-carbalkoxyamino-4-phenoXymethyl-5-hydroxymeth yl-pyridine (IV) already at comparatively low temperatures not only the phenoxy radical can be saponified by treatment with hydrogen bromide, but also the urethane in one step. Thereby, 2-methyl-3-amino-4,5-dibromo-methyl-pyridine-hydrobromide is obtained. By the action of water and nitrous acid or materials easily developing nitrous acid, it can readily be converted into adermin (VI, 2-methyl-3-hydroxy-4,5-dihydroxymethyl-pyridine) by heating.

I have also found that the aforementioned 2- methyl-4-phenoxymethyl-5-cyano-6-chloro-pyridine-3-carboxylic acid chloride (11) can be directly converted into the azide by treatment with sodium azide, and that 2-methyl-3-carbalkoXy-amino-4-phenoxymethyl-5-hydroxymethyl-pyridine (IV), may be sapomfied with diluted HCl at elevated temperatures and thentreated with nitrous acid or materials developing nitrous acid, for instance, silver nitrite.

It is to be noted that the various conversions of the different groups may occur in one step, for instance, the formation of the acid chloride in 3 position may be accomplished together with the conversion of the hydroxy group in 6 position into the halogen (chlorine) pyridine derivative. It can be done by acting upon the 2-methyl-4- phenoxymethyl-5-cyano-6-hydroxy pyridine-3- carboxylic acid with phosphorus pentachloride.

Furthermore, the hydrogenation of the cyano group into the amino methyl group may take place concurrently with the substitution of the halogen by hydrogen, or the splitting off of the phenoxy radical by saponification may occur simultaneously with the saponification of the urethane into the amine.

Example I 20 parts by weight of 2-methyl-4-phenoxymethyl-5-cyano- 6-hydroxypyridine-3-carboxylic acid are heated with 35 parts by weight of phosphorus-pentachloride and 50 parts by weight of phosphorus-oxychloride or with another indifferent solvent under reflux until all has gone into solution and the hydrogen chloride evolution has ceased. The solvent and the phosphorus-oxychloride formed are distilled ofi in vacuo as completely as possible and the crystalline residue, representing the acid chloride of Z-methyll-phenoxymethyl-5- cyano 6 chloropyridine 3- carboxylic acid, taken up in about 200 parts by volume of warm benzene. A solution of '7 parts by weight of hydrazine-hydrate in 100 parts by volume of a 10% solution of caustic soda is added dropwise to the benzene solution of the acid chloride while stirring, whereby the temperature is suitably kept below 30 C. Finally, another 50 parts by volume of a 10% solution of caustic soda are added and the mixture allowed to stand for minutes. removed from the benzene layer and acidified whereby the hydrazide separates as a brownish, crystalline precipitate.

For the purpose of purification the product can be triturated with dilute ammonia and sucked off. Following this, it can be recrystallized from ethyl-acetate-petroleum ether.

2-methyl-4-phenoxymethyl-5-cyano- 6 chlo ropyridine-3-carboxylic acid hydrazide is a colorless crystalline powder of melting point 114-115 C. It is easily soluble in alcohol and ethyl acetate, difiicultly soluble in the cold in benzene and ether. It is difiicultly soluble in water or petroleum ether.

The brownish aqueous layer is 4 In dilute alkalis it is easily soluble and can be re precipitated by addition of an acid, ammonium salts or acid salts.

10 parts by weight of 2-methyl-4-phenoxymethyl-5-cyano 6 chloropyridine-3 carboxylic acid hydrazide are dissolved in 50 parts by volume of absolute'alcohol, a few drops of alcoholic hydrochloric acid and 5 parts by weight of amylnitrite added.

Crystalline precipitation of the azide quickly sets in, going into solution upon gentle heating with evolution of nitrogen. When the evolution of nitrogen has come to an end, the product is: concentrated whereby 2-methyl-3-carbethoxy amino-4-phenoxymethyl-5- cyano- 6- chloropyr-- idine separates on cooling in the form of crystal-- line needles. For purification purposes the prod-- not is recrystallized from a little alcohol or from. benzene. The melting point is at 167 C.

12 parts by weight of 2-methyl-3-carbethoxyamino-4-phenoxymethyl-5-cyano-6 ch1oropyri-- dine are stirred up with 120 parts by weight of methanol, 12 parts by weight of 25% aqueous: ammonia and 1.2 parts by weight of a nickelcatalyst (Raney nickel) in a hydrogenation-- autoclave at a gauge pressure of 20 atm. and, simultaneously slowly heated to 60 C. 3 mols of hydrogen are quickly taken up whereupon the: hydrogenation is completely finished. The prod-- uct is allowed to cool, separated from the catalyst. and the entirely colorless filtrate dried in vacuo.. The residue is taken up in 100 parts by volume of. water, small quantities of undissolved material. filtered off, the filtrate rendered acid to Congo paper with dilute hydrochloric acid and again: evaporated to dryness in vacuo. The residue is; recrystallized from ethanol. The resulting (ii-- hydrochloride of 2-methyl-3-carbethoxyamino-4-' phenoxymethyl-5-aminomethyl-pyridine melts at.

238 C. The yield amounts to of the theoret-- ical.

10 parts by weight of 2-methy1-3-carbethoxy-- aminol-phenoxymethyl 5 amino-methylpyri-- dine-hydrochloride are dissolved in parts byvolume of 5% hydrochloric acid, the solution.

' C. After the evolution of nitrogen and oxides of.

nitrogen has ceased the product is allowed to cool and rendered alkaline with ammonia. The compound first separates as an oil and becomes crystalline on standing. It is sucked off and recrystallized from benzene. 2-methyl-3-carbethoxyamino -4 phenoxymethyl- 5-h y d r o x ymethyl-pyridine forms white prismatic needles of melting point 127 C.

4 parts by weight of 2-methyl-3-carbethoxyamino 4-phenoxymethyl-5-hydroxymethylpyri-- dine are heated with 40 parts by volume of hydro-- bromic acid (about 50%) for 10 minutes at 65-70 C. until the CO2 development is terminated. The. product is now evaporated in vacuo almost to dry ness, allowed to crystallize overnight and taken up with alcohol in which the bromo-compound is difiicultly soluble and is sucked off. By concentration of the mother liquor further quantities of the bromo-compound are obtained.

This is dissolved in 100 parts by volume of water and boiled for 20 minutes. Thereupon 10 parts by volume of 3 -n hydrochloric acid are added and 1.5 parts by weight of freshly prepared silver nitrite quickly added while stirring at 90 C. After the cessation of evolution of nitrogen and oxides of nitrogen the product is filtered off from silver bromide and silver chloride and concentrated in vacuo. The residue crystallizes spontaneously, if need be upon rubbing with acetone, and proves to be Vitamin Be-hydrochloride (adermin) of melting point 206-207" C.

Example II 32 parts of the 2-methyl-4-phenoxymethyl-5- cyano-6echloro-pyridin-3-carboxylic acid chloride melting point 155-157 which has been prepared according to Example I are dissolved by 200 parts by volume dioxane while stirring. The

solution is cooled to 5 C. and is dropped at that,

worked up into adermin, both as in Example I.

Example III 31.5 parts of 2-methyl-4-phenoxymethyl-S-hydroxymethyl-pyridine-3-urethane are heated in 500 parts of 2.5% hydrochloric acid to 170-180" C. for 5 hours. The brown solution is decolorized with animal charcoal and is stirred up with 18 parts silver nitrite at -80 C. The silver chloride is filtered ofi and the solution is concentrated in vacuo during which time adermin crystallizes from the solution.

This application is a division of my earlier application Serial Number 409,298, filed September 2, 1941.

What I claim is:

1. The compound 2-methyl-3-carbalkoxyamino-4-phenoxymethyl-5-aminomethylpyridine.

2. The compound 2-methyl-3-carbethoxyamino-4-phenoxymethyl-5 aminomethyl pyridine, having a melting point of about 238 C.

MAX HOFFER. 

